Remove the redundant libcutils_sockets_test

'sockets_test.cpp' also runs as part of libcutils_test and
libcutils_static_test, so it is redundant to have it be a separate
target.

Test: libcutils_test
Test: libcutils_static_test
Bug: 317884162
Change-Id: Ib2c2f74feb79d1436ca67ae9aca18d3eb7acf5a0